1. Field of the Invention
The present invention relates to a thermal decomposition system for thermally decomposing ash discharged from incinerators, sludge, and wastes discharged from companies' facilities, etc. Particularly, the invention is concerned with a thermal decomposition system capable of thermally decomposing even such industrial wastes as rubber and plastic products which produce poisonous gases during incineration.
2. Description of the Prior Art
Wastes discharged from homes and companies' facilities have heretofore been classified mainly into combustible refuses capable of being incinerated, incombustible refuses incapable of being incinerated because of issuing of poisonous gases upon incineration, such as rubber and plastic products, resource refuses capable of being recycled such as paper, glass and aluminum products, and industrial wastes such as waste oils, concrete and metallic structures discharged from factories and facilities. These refuses and wastes are subjected to respective appropriate treatments and disposals.
Generally, combustible refuses are subjected to incineration, while incombustible refuse is buried in landfill spaces. As to resource refuses, they are classified according to the materials of paper, glass, aluminum, etc. and the thus-classified materials are subjected to crushing or melting for recycling. Further, industrial wastes are subjected to respective appropriate special processings.
However, as to some wastes, incineration is not accepted as is the case with rubber and plastic products even if they are combustible. Besides, those wastes issue smokes and gases due to, for example, incomplete combustion during incineration, exerting a bad influence on the environment. Moreover, in the conventional incinerators, wastes are incinerated by burning in air, so if a chlorine-containing waste is mixed therein, dioxin and chlorine compounds will be produced, thus giving rise to the problem that a bad influence is exerted on the environment.
Further, since ash from incineration and incombustible refuses incapable of being subjected to incineration are buried in landfill spaces, etc., it is necessary to ensure landfill spaces. Besides, offensive smells emitted from wastes and heavy metals contained in wastes exert a bad influence on the environment which surrounds the landfill space concerned.
The applicant in the present case has developed a thermal decomposition system wherein wastes to be treated are put into a hermetically sealed crucible, then the interior of the crucible is made vacuous and heating is conducted to thermally decompose the wastes, and obtained a patent for that system (Japanese Patent Publication No. 34902/95, U.S. Pat. No. 2,038,214).
In the said thermal decomposition system, a crucible which contains wastes to be incinerated is supported within a furnace body so as to give a clearance between an inner wall of the furnace body and an outer wall of the crucible except the supported portion of the crucible, a heating device for heating the crucible is mounted in the clearance between the inner wall of the furnace body and the outer wall of the crucible, an opening of the crucible is positioned inside an opening of the furnace body, an opening/closing lid for closing those openings at a time and a suction pipe for discharging gases produced during incineration of the materials to be treated from the interior of the crucible are provided, and further provided are a suction device connected to the suction pipe and a gas sorting/extracting device connected to the suction device. The interior of the crucible is closed with the opening/closing lid and is made vacuous, then in this vacuous state the wastes to be treated present in the interior of the crucible are heated, and gases produced from the wastes are withdrawn from the crucible by the suction device and are extracted by the gas sorting/extracting device.
However, according to the system being considered, wastes to be treated can be charged into the crucible only in a predetermined certain quantity, so the work comprising sealing the crucible interior hermetically, making it vacuous, heating, and withdrawal after the heating for a certain time, must be repeated for each predetermined quantity of wastes. Therefore, in the case where the volume of wastes to be treated is large, it is necessary that a series of operations be repeated many times, and thus much time and labor are required.